In the 1960s, the art historian Roy Strong spotted distinct similarities in a string of anonymous pictures. They dated to 16th-century Britain and shared the same strong hand. Female sitters were always painted at half-length, turning out towards the left. All subject had flushed cheeks and crisply outlined eyes and mouths. Though the name of the artist has never been discovered, he or she was given the title of the “Master of the Countess of Warwick,” which was based on a 1569 painting of the noblewoman Anne Russell. The artist painted men, women, children, and teens in pantaloons, lace bodices, and neck ruffs—hallmarks of the era. This exhibition includes an unprecedented array of work by the mysterious master. Arresting portraits by Hans Eworth round out the show. —Elena Clavarino